I thought there might be issue with internet connection, but I am able to open few websites from within MyEclipse using MyEclipse browser. Update websites are also correct as I copied them from their websites only.
Not sure why you're trying to install m2eclipse, as m2eclipse functionality is already integrated into MyEclipse. Installation may conflict with what is already there.
You said you could open a few websites but did you try the website that contains the JiBX plugin? You'll probably get some kind of error in a browser (like 404) but it should at least indicate that you've connected to the site.
subject: Unable to install couple plugins on MyEclipse